1. Field of the Invention
The present invention relates to a solar panel which is mounted to an artificial satellite or a space station, for example, for use in space.
2. Description of Related Art
FIG. 27 is a schematic view showing a conventional artificial satellite 1. As shown in FIG. 27, the artificial satellite 1 uses space solar panels 3, and has solar paddles 2, which protrude like wings from the left and right of a substantially cylindrical artificial satellite body 5 and are used as a power source of the artificial satellite body 5.
The solar paddle 2 is composed of solar panels 3 which are connected with one another via hinges, which solar panels are integrally structured units that are not allowed to be folded. The electrical circuit of the solar panel 3 is usually connected directly to a bus line. The solar panel 3 is normally about 3 mxc3x973.5 m in size and made up of several thousands to several tens of thousands of solar cells. The artificial satellite 1 is transported into space with the solar paddle 2 stored (folded up), and then spread out when the artificial satellite 1 reaches space.
FIG. 28 is an enlarged front view of section S28 (solar panel portion) of the solar paddles 2 in FIG. 27. As shown in FIG. 28, a large number of solar cells 4 are attached to the surface of the solar panels 3. FIG. 29 is an enlarged front view of section S29 of the solar panel 3 of FIG. 28. As shown in FIG. 29, the solar cells 4 are arranged in a matrix form and connected to one another by a current path 6 for collecting generated electricity. The solar cells 4 are provided with cover glass sheets 7, and to prevent the cover glass sheets 7 from being charged by cosmic rays, for example, they are connected to ground wires 8, which are connected to the satellite ground of the artificial satellite 1.
FIG. 30 is across sectional view taken along the section line Axe2x80x94A of FIG. 29. The solar cells 4 are fixed to a support plate (substrate) 11 by an adhesive 10. The solar cells 4 have a solar cell body 9 and a cover glass sheet 7, which is attached to the light receiving side of the solar cell body 9. The support plate 11 is a honeycomb-structure made of aluminum, for example, and the solar cells 4 are attached to the surface of the support plate.
This type of conventional space solar panel 3 is disclosed in Japanese Unexamined Patent Publication JP-A 6-275857 (1994), for example. In an ordinary solar panel, as represented by this disclosure, several thousand to several tens of thousands of solar panels that are approximately 4 cmxc3x976 cm, for example, are arranged on a support plate (substrate) with a honeycomb structure made of aluminum. Furthermore, conductive links called inter-connectors, which electrically connect the solar cells to one another, are sandwiched between the solar cells and the surface of the support plate.
The cover glass sheets, which are provided tightly adhered to the light-receiving surface of the solar cells, are coated with a conductive film, and are linked by conductive linking wiring that electrically connects them to one another.
At this time, an irreversible connection technique such as welding or soldering is used as the method for electrically connecting the solar cells to the conductive links, and for electrically connecting each cover glass sheet to the conductive linking wiring. Moreover, an irreversible connection method using an adhesive, for example, is used also as means for disposing the solar cells and the conductive links on the support plate.
Irreversibly connecting the components that configure the solar panel in this way ensures that they are highly reliable with respect to vibration generated during the artificial satellite""s transport into space and in the environment of space.
With this conventional technique, the manufacturing of a solar panel for space includes the task of adhering all of the several thousand to several tens of thousands of solar cells making up the solar panels to the support plate with an adhesive. Moreover, the task of electrically connecting all of the wiring for electrically connecting the solar cells and for electrically connecting the cover glass sheets, which are closely adhered to the light receiving surface of the solar cells, is performed by welding or soldering.
Conventional solar panels for space are large and come in various shapes depending on their intended uses, and thus it is difficult to manufacture solar panels on an automated production line. Consequently, complex process steps and an enormous amount of time are required to manufacture solar panels for space.
Furthermore, almost all components making up conventional space solar panels are joined together with an irreversible method, and therefore when problems, such as when the solar cells are damaged during the manufacturing or assembly steps, required solar panel repair work involving the replacement of solar cells, performing this replacement work is extremely difficult.
Replacement work involves first electrically disconnecting the solar cell from the solar panel by severing the metal wiring (inter-connector) that is welded, for example, between the solar cells to electrically connect them to one another. Next, the adhesive on the backside of the solar cell is cut and the solar cell is stripped from the solar panel. Then, a new solar cell slightly smaller than the created space is adhered to the stripped away space using an adhesive, and the wiring is reconnected by welding. The repair of solar panels involved performing these complex process steps.
This series of tasks is performed with respect to all of the numerous solar cells mounted on all regions of a solar panel each time a problem occurred, and becomes a large amount of work depending on the extent of the repair.
Furthermore, the increase in the size of artificial satellites has recently given rise to a demand for solar cells with a high photovoltaic efficiency, and thus the material for solar cells has changed from conventional silicon (Si) to III-V semiconductors such as gallium arsenide (GaAs). Normally, the crystal of III-V semiconductors is brittle and easily broken, and solar cells using such material have a higher percentage of cracking or chipping than Si solar cells. Even with conventional methods for manufacturing solar panels, this change to III-V semiconductors as the material for solar cells leads to an increased frequency of solar cell replacement or repair resulting from cracks in the solar cells.
Furthermore, heretofore the above-mentioned replacement work was performed on earth during the stage of manufacturing the solar panel or attaching it to the satellite. However, due to the recent progress in space technology, the environment is becoming one in which human beings can reside and work in space over comparatively long periods of time, for example collecting artificial satellites using manned space shuttles or performing feasibility experiments of manned space stations, and the possibility of performing repairs in space, which heretofore were physically difficult, has increased. With conventional methods, however, a large amount of complex tasks, like those mentioned above, is required in repairing a solar panel, and thus for all practical purposes performing repairs in space was impossible.
In light of these circumstances, it is an object of the invention to provide a solar panel for use in space and a method for manufacturing the same, with which the solar panel for use in space can be manufactured easily and in short time, and replacement or repair work on solar cells can be performed easier and less expensively in time.
The invention provides a solar panel for use in space comprising a plurality of unit solar cell modules including a plurality of solar cells and connection wires for connecting the solar cells, wherein an entirety of the solar panel for use in space is configured by linking the plurality of unit solar cell modules and the linking of the unit solar cell modules electrically connects the unit solar cell modules to one another.
According to the invention, unit solar cell modules including a plurality of solar cells can be combined to form a solar panel for use in space. Consequently, it is possible to easily form solar panels with different power generation properties or shapes by changing the combination of the unit solar cell modules. The manufacture of standardized unit solar cell modules can be automated for mass production, and thus the manufacture of the solar panels can be performed easily and in shorter time.
The unit solar cell modules are provided with electrical wiring, and by mechanically linking the unit solar cell modules to one another they can also be connected electrically. Therefore, a process step for electrically connecting the unit solar cell modules is not necessary, and thus work in the assembly and repair of solar panels can be shortened to reduce overall work time.
In accordance with the invention, solar panels with different power generation capabilities and sizes can be easily fabricated by combining standardized unit solar cell modules to configure the solar panels. Furthermore, using the same standardized unit solar cell modules in a variety of different solar panels makes it possible to mass produce the unit solar cell modules in automated production lines.
Because the unit solar cell modules can be electrically connected by mechanically linking them to one another, the number of steps required to assemble the solar panels is reduced, which in turn reduces task-related mistakes, and therefore highly reliable solar panels for use in space can be manufactured efficiently.
In the invention it is preferable that the unit solar cell modules are linked by detachable means.
According to this aspect of the invention, the unit solar cell modules are detachably attached to the solar panels. Consequently, it is possible to easily remove only damaged unit solar cell modules, for example, and repairs or adjustments with respect to the solar panels can be performed without difficulty.
With this aspect of the invention, when the solar cells are damaged, it is possible to easily remove and replace only the damaged unit solar cell module, and thus the degree of difficulty of repair work on solar panels in space, for example, can be reduced. Also, work efficiency can be improved when repairing the solar panels during manufacture or thereafter.
In the invention it is preferable that a bypass diode for protecting the solar cells with respect to a reverse bias is installed in the unit solar cell modules.
According to this aspect of the invention, the unit solar cell modules have a bypass diode. Consequently, when solar cells are hidden by the shadow of the satellite body and can no longer generate power, or when solar cells are unable to generate power due to damage and/or dirtiness of the cells themselves, the electrical current flows through the diode and bypasses these cells, and thus damage to the solar panel resulting from solar cells with lowered power generating capabilities can be suppressed to a minimum.
With this aspect of the invention, providing bypass diodes in the unit solar cell modules can prevent damage to the solar cells caused by a reverse bias. The damage of broken solar cells can also be minimized. Therefore, unit solar cell module reliability can be improved, and the unit solar cell modules can be used in places such as space, where replacement or repairs are difficult to perform.
In the invention it is preferable that the unit solar cell modules have a support plate with a honeycomb structure of which principal material is aluminum, and that the solar cells are fastened to this support plate.
According to this aspect of the invention, the unit solar cell modules have a support plate, and by fastening the solar cells to the support plate, the strength of the unit solar cell modules can be improved. Moreover, the support plate has a honeycomb structure and is made of aluminum, and thus the unit solar cell modules can be kept lightweight yet sufficiently strong.
With this aspect of the invention, the solar cells are fastened to the support plate, thereby improving the rigidity of the unit solar cell modules. Consequently, there is a reduced risk that the solar panels will be damaged by the acceleration and vibration that occur during transport into space. The support plate is made of aluminum material that has a honeycomb structure, and thus the unit solar cell modules can be kept lightweight yet sufficiently strong.
In the invention it is preferable that the entire of the solar panel is configured by fitting the unit solar cell modules into accommodating spaces for accommodating the unit solar cell modules which are provided in a frame body.
According to this aspect of the invention, the unit solar cell modules are fitted into the accommodating spaces of the frame body, thereby fastening them to the frame body and inhibiting vibration as well as improving the rigidity of the entirety of the solar panel. The unit solar cell modules can be easily positioned, and thus the solar panels can be easily assembled without making a mistake regarding the arrangement position for the unit solar cell modules.
With this aspect of the invention, the unit solar cell modules are prevented from vibrating because they are fitted into the frame body, and thus the rigidity of the entirety of the solar panel is improved. Consequently, there is a reduced risk that the solar panels will be damaged by vibration and acceleration during the transport into space. Furthermore, because the unit solar cell modules are fitted into the frame body, the task of positioning the unit solar cell modules is easy, and thus the solar panels can be assembled with ease.
In the invention it is preferable that the entirety of the solar panel is configured by arranging and linking together the unit solar cell modules on a substrate on which the arrangement positions for the unit solar cell modules are indicated.
According to this aspect of the invention, because the unit solar cell modules are connected to the arrangement positions on the substrate, the time required for positioning them is shortened. Also, the easily damaged solar cells are reinforced by the substrate, and thus the solar cells can be further prevented from breaking.
With this aspect of the invention, the unit solar cell modules are connected to the arrangement positions on the substrate, and thus the unit solar cell modules are reinforced by the substrate, and the solar cells can be prevented from being damaged.
In the invention it is preferable that the unit solar cell modules have a structure with which they can be mechanically linked to one another, and that the entirety of the solar panel is configured by mechanically linking the unit solar cell modules to one another.
According to this aspect of the invention, a solar panel can be easily assembled by mechanically linking a plurality of unit solar cell modules to one another, and the unit solar cell modules can be more reliably linked to one another.
In the invention it is preferable that the unit solar cell modules have a structure with which they can be mechanically linked to one another, and that an entirety of the panel is configured by fitting a plurality of mutually linked unit solar cell modules into a frame body provided with accommodating spaces for accommodating a plurality of mutually linked unit solar cell modules.
According to this aspect of the invention, a plurality of mutually linked unit solar cell modules are fitted into the accommodating spaces of the frame body, thereby fastening the unit solar cell modules to the frame body and improving the rigidity of the entirety of the solar panel.
In the invention it is preferable that the mechanical structure linking the unit solar cell modules to one another includes a protruding portion provided on one side of each of the unit solar cell modules and a recessed portion provided on another side of each of the unit solar cell modules.
According to this aspect of the invention, the protruding portion of one unit solar cell module can be interlocked with the recessed portion of another unit solar cell module to easily join and link up any number of unit solar cell modules. Moreover, because the protruding portions and the recessed portions interlock, there is no risk of linking the unit solar cell modules together facing in the wrong direction.
With this aspect of the invention, by providing a protruding portion on one side and a recessed portion on the other side of each of the unit solar cell modules, a plurality of unit solar cell modules can be mechanically linked to each other. Consequently, there is no risk of linking the unit solar cell modules together facing in the wrong direction, and they can be linked together with ease in places such as space where it is difficult to perform complex tasks.
In the invention it is preferable that the frame body includes ground conduction paths for electrically connecting a light receiving side surface of each of the unit solar cell modules to a spacecraft ground.
According to this aspect of the invention, the light receiving side surface of each of the unit solar cell modules can be kept from being charged due to cosmic rays by connecting the light receiving side surface of the unit solar cell modules with the ground conduction paths to a ground.
With this aspect of the invention, the surfaces of the solar panels can be prevented from being charged by connecting the light receiving surface side of the unit solar cell-modules to a ground.
In the invention it is preferable that a plurality of unit solar cell modules interconnected is lined with a resin film.
According to this aspect of the invention, lining the unit solar cell modules with a resin film improves the strength of the solar panels while keeping them lightweight.
With this aspect of the invention, by lining the unit solar cellmodules with a resin film, it is possible to improve the strength of the solar panels while keeping them lightweight.
In the invention it is preferable that the unit solar cell modules are provided with condenser lenses for gathering light into the solar cells.
According to this aspect of the invention, the solar cells can receive the light gathered by the condenser lenses, and thus can more effectively convert light energy into electrical energy. Consequently, the area of the solar cells can be kept smaller than the light receiving area of the solar panel itself. Thus, the solar panels can be made small and lightweight, and the number of expensive semiconductor cells that are used can be kept low.
The arrangement of the condenser lenses and the solar cells is adjusted in the unit solar cell modules, and therefore when the solar panels are assembled, it is not necessary to once again adjust the positions of condenser lenses and the solar cells.
Furthermore, with this aspect of the invention, the condenser lenses can focus solar light, and thus it is possible to reduce the size of the solar cells, keep down the used amount of semiconductors, and lower costs. The unit solar cell modules have a set arrangement of condenser lenses, so when assembling the solar panel, it is not necessary to adjust the positions of the condenser lenses and the solar cells, and thus the solar panel can be easily assembled.
In the invention it is preferable that the unit solar cell modules are provided with a frame for supporting the condenser lenses, the solar cells, and the connection wires.
According to this aspect of the invention, the frame holds the condenser lenses with sufficient strength and the solar panels can be made lightweight.
With this aspect of the invention, the frame can hold the condenser lenses with sufficient strength.
In the invention it is preferable that the condenser lenses have a plurality of non-consecutive focal points with respect to a single lens plate, and that the solar cells are arranged at positions corresponding to those focal points.
According to this aspect of the invention, the condenser lenses have a plurality of focal points, so it is not necessary to provide a condenser lens for each solar cell that is disposed in a unit solar cell module, and when there are for example nine solar cells disposed in a unit solar cell module, it is sufficient to attaching only one lens plate having nine focal points, thus making it is possible to reduce the number of components in the unit solar cell modules compared to the case in which nine lens plates each with a single focal point are attached.
With this aspect of the invention, the condenser lenses have a plurality of focal points, so it is not necessary to provide a condenser lens for each solar cell that is disposed in a unit solar cell module, and thus the number of components in the unit solar cell modules can be reduced. Therefore, the unit solar cell modules can be fabricated more easily.
In the invention it is preferable that the connection wires and a bypass diode for protecting the solar cells with respect to a reverse bias are disposed in regions which are not irradiated with light gathered by the condenser lenses.
According to this aspect of the invention, the connection wires and the bypass diode are provided in regions which are not irradiated with light, and thus they do not deteriorate due to light, and their lifetime can be prolonged.
With this aspect of the invention, the connection wires and the bypass diode are provided in regions where light is not gathered, and thus they do not deteriorate due to the light, and their lifetime can be prolonged. Therefore, the reliability of the solar panel increases, and it can be used in places like space where it is difficult to perform replacement or repair work.
In the invention it is preferable that a surface of the condenser lenses is coated with a light transmitting, conductive thin film that is connected to a spacecraft ground.
According to this aspect of the invention, the conductive thin film can suppress a charging of the surface of the condenser lenses due to cosmic rays.
With this aspect of the invention, because the conductive thin film is connected to a ground, the surface of the solar panel can be kept from becoming charged, and thus problems due to such charging can be prevented.
In accordance with the invention, a method for manufacturing a solar panel for space use includes:
configuring an entirety of the solar panel for use in space by detachably linking a plurality of unit solar cell modules, which include a plurality of solar cells and connection wires for connecting the solar cells, connecting the unit solar cell modules to one another, and
repairing or adjusting the solar panel by removing and exchanging a portion of the linked unit solar cell modules.
According to this aspect of the invention, the unit solar cell modules are detachably linked to a solar panel, so by removing and replacing unit solar cell modules including broken solar cells, repair work on the solar panel can be simplified and work time can be reduced.
Because the unit solar cell modules are detachably linked to a solar panel, maintenance on the solar panel can be performed by removing and replacing unit solar cell modules including broken solar cells.
Thus, work such as repairs or maintenance resulting from the replacement of solar cells can be easily carried out with less amount of work than conventionally, and can be suitably adapted to maintenance performed in space, which has conventionally been considered difficult.